Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $31,000 Total Non-Federal Funds: $62,000
Abstract: Connected and functioning alluvial floodplains have the potential to reduce flood risk todownstream communities by attenuating peak discharges. Floodplains are also valued for theirecosystem functions including sediment and nutrient storage, groundwater recharge, and supportto aquatic and riparian habitats. Low-complexity topographic and hydrologic modeling isunderway across the Vermont portion of the Lake Champlain basin to better define thegeographic extents of floodplain inundation, as well as the frequency, duration and timing offlooding events that influence the water, sediment and nutrient storage potential and associatedbiogeochemical functions of floodplains. Low-complexity models sacrifice detail andrepresentation of hydrodynamic processes in favor of application over regional scales. Due totheir necessary reliance on coarse-resolution and remote-sensing data sets and simplifiedempirical relationships, these modeling approaches can misrepresent inundation extents where channel and floodplain features have been locally modified. New assessment approaches are needed that incorporate reach-scale stream geomorphic data with low-complexity hydraulicmodels to understand the degree to which vertical-lateral (dis)connection (e.g., channel incisionand encroachment leading to enhanced entrenchment) has contributed to (over)underestimatedinundation extents. We propose a pilot study in the Mad River watershed of the Lake Champlainbasin to integrate existing stream geomorphic assessment data with probabilistic inundationmapping to better interpret the influence of reach-scale channel-floodplain configurations onfloodplain function and flooding risk. These enhanced low-complexity modeling approaches2will generate more accurate estimates of inundation extents and depths. Better information onthe extent, timing and duration of lateral flows will inform estimates of floodplain function forwater and sediment/nutrient storage, biogeochemical cycling, and support to aquatic andterrestrial habitats.